What Are Hair Cells in the Ear ?
What are hair cells in the ear ?
Hair cells are the nerve receptors of the ear that respond to sound. When sound travels deep into ear, it enter the organ of hearing, the cochlea where a chain of physical events occurs that causes the hair cells to bend. This creates a biochemical change in the cells that eventually triggers an impulse to the hearing nerve which then travels up to the brain.
Two types of hair cells
There are two types of hair cells in the hearing organ; inner hair cells and outer hair cells. Outer hair cells are referred to as an “amplifier” because they make soft sounds more audible. There are approximately 15,000 outer hair cells in the human ear. Once these cells die due to aging, noise exposure, disease or poor development, sound has to be much louder to be heard. Inner hair cells convert sound to a neural impulse so that the auditory nerve (VIIIth cranial nerve) can relay sound to the brain. There are approximately 3,500 inner hair cells. Damage to inner hair cells is believed to contribute to poor ability to understand speech as well as make it difficult to recognize tonal quality to music.
Hair Cell Regeneration and Research
Once hair cells are damaged in mammals they do not grow back, which results in permanent, irreversible hearing loss. However, birds and some reptiles are able to regenerate hair cells. It is not understood how this done although research is exploring the mechanisms behind this. Other studies are exploring gene therapy (ways to stimulate hair cell growth from other cells or dead hair cells) and transplants of hair cells.
Hearing and Hair Cells-The Basement
NOHR Foundation: Inner Hair Cell Regeneration